I have a busy light rail train within 50' of my house, which used to cause skipping at times with my other tables. I have a Target-like open metal and mdf rack that sits on a suspended wooden floor over a garage. The 85-year-old building, like most western San Francisco real estate, is built on a thin veneer of concrete and blacktop sitting on former sand dunes, which are inherently unstable. I've been here for 8 years, so have done a lot of experimentation with inner tubes, springs, foam, mag lev, and different types of shelving made of wood, acrylic, mdf, in various combinations.
First, I found the most significant improvement by first locating the rack where there is the greatest stability in the first place - so I'd suggest finding out whether there is a better location either on the wall furthest from the biggest source of vibrations, or somewhere on the existing wall that is less susceptible to vibrations.
For me, what made the skipping go away without any sonic side effects is the following. If this worked for me and you have less vibration than me to address, it may be just the ticket to reduce feedback below perceptibility:
1. Sorbothane pucks between the metal rack and the mdf shelf
2. Adding a 4" hard maple butcher block on top of the mdf shelf, with a large piece of recycled rubber crumb mat between the block and the shelf
http://www.grainger.com/product/10U465?cm_sp=HIO-_-HIDP-_-RR_VTV_P&cm_vc=IDPRRZ11&zoneId=IDPRRZ113. Herbie's turntable footers or tall Tenderfeet (soft), on top of a thick fat dot (dB neutralizer), on top of a piece of Grungebuster (regular thickness). The Tenderfeet work better with more severe vibrations, but can overdamp the sound compared to the turntable-specific footers. I recommend using 4 footers or 4 Tenderfeet.
4. The rack itself sits on Herbie's large gliders.
The above worked best after trying out different combos. I can now jump and stomp right next to the rack, and there is a significant reduction in feedback through the table. Though with this "torture test" low frequency rumble does slightly break through the music, it does not cause concern or worry that it would come even close to making the stylus skip, and it is much less audible than if I bumped into the table or rack accidentally.
I never tried hanging the table from the ceiling, but this was my last, untried project mostly due to concerns with stability. Very, very low WAF in any case.